// Copyright (c) 2012 The Chromium Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

#include "ui/base/dragdrop/drag_utils.h"

#include <objidl.h>
#include <shlobj.h>
#include <shobjidl.h>
#include <stddef.h>

#include "base/win/scoped_comptr.h"
#include "base/win/scoped_hdc.h"
#include "third_party/skia/include/core/SkBitmap.h"
#include "ui/base/dragdrop/os_exchange_data.h"
#include "ui/base/dragdrop/os_exchange_data_provider_win.h"
#include "ui/gfx/canvas.h"
#include "ui/gfx/gdi_util.h"
#include "ui/gfx/geometry/size.h"
#include "ui/gfx/image/image_skia.h"
#include "ui/gfx/skbitmap_operations.h"

namespace drag_utils {

static void SetDragImageOnDataObject(HBITMAP hbitmap,
    const gfx::Size& size_in_pixels,
    const gfx::Vector2d& cursor_offset,
    IDataObject* data_object)
{
    base::win::ScopedComPtr<IDragSourceHelper> helper;
    HRESULT rv = CoCreateInstance(CLSID_DragDropHelper, 0, CLSCTX_INPROC_SERVER,
        IID_IDragSourceHelper, helper.ReceiveVoid());
    if (SUCCEEDED(rv)) {
        SHDRAGIMAGE sdi;
        sdi.sizeDragImage = size_in_pixels.ToSIZE();
        sdi.crColorKey = 0xFFFFFFFF;
        sdi.hbmpDragImage = hbitmap;
        sdi.ptOffset = gfx::PointAtOffsetFromOrigin(cursor_offset).ToPOINT();
        helper->InitializeFromBitmap(&sdi, data_object);
    }
}

// Blit the contents of the canvas to a new HBITMAP. It is the caller's
// responsibility to release the |bits| buffer.
static HBITMAP CreateHBITMAPFromSkBitmap(const SkBitmap& sk_bitmap)
{
    base::win::ScopedGetDC screen_dc(NULL);
    BITMAPINFOHEADER header;
    gfx::CreateBitmapHeader(sk_bitmap.width(), sk_bitmap.height(), &header);
    void* bits;
    HBITMAP bitmap = CreateDIBSection(screen_dc, reinterpret_cast<BITMAPINFO*>(&header),
        DIB_RGB_COLORS, &bits, NULL, 0);
    if (!bitmap || !bits)
        return NULL;
    DCHECK_EQ(sk_bitmap.rowBytes(), static_cast<size_t>(sk_bitmap.width() * 4));
    SkAutoLockPixels lock(sk_bitmap);
    memcpy(
        bits, sk_bitmap.getPixels(), sk_bitmap.height() * sk_bitmap.rowBytes());
    return bitmap;
}

void SetDragImageOnDataObject(const gfx::ImageSkia& image_skia,
    const gfx::Vector2d& cursor_offset,
    ui::OSExchangeData* data_object)
{
    DCHECK(data_object && !image_skia.size().IsEmpty());
    // InitializeFromBitmap() doesn't expect an alpha channel and is confused
    // by premultiplied colors, so unpremultiply the bitmap.
    // SetDragImageOnDataObject(HBITMAP) takes ownership of the bitmap.
    HBITMAP bitmap = CreateHBITMAPFromSkBitmap(
        SkBitmapOperations::UnPreMultiply(*image_skia.bitmap()));
    if (bitmap) {
        // Attach 'bitmap' to the data_object.
        SetDragImageOnDataObject(
            bitmap,
            gfx::Size(image_skia.bitmap()->width(), image_skia.bitmap()->height()),
            cursor_offset,
            ui::OSExchangeDataProviderWin::GetIDataObject(*data_object));
    }

    // TODO: the above code is used in non-Ash, while below is used in Ash. If we
    // could figure this context out then we wouldn't do unnecessary work. However
    // as it stands getting this information in ui/base would be a layering
    // violation.
    data_object->provider().SetDragImage(image_skia, cursor_offset);
}

} // namespace drag_utils
